1. Field of the Invention
The present invention relates to wireless communications networks, and, more particularly, to a personal communications network (PCN) and system architecture that enables integration of personal communications networks (PCN) and digital cellular networks (DCN).
2. Description of Related Art
A digital cellular network (DCN) is a mobile wireless telephone service in which radio coverage is divided into a network of cells and each cell is assigned a number of available radio frequencies. In the standard DCN, a base station transceiver system (BTS) transmits and receives control and voice communication information from a base station controller (BSC) within the same cell, and transfers the information to selected mobile users within the cell via a radio interface, such as, for example, the E-TDMA radio interface proposed by Hughes Network Systems, Inc. The base station controller (BSC) is controlled by a mobile switching center (MSC) that provides an interface to a public switched telephone network (PSTN) interface, and which provides mobility control across the cellular network. The mobile switching center (MSC) controls the transfer of communications information to selected base station controllers within the cellular network according to the position of the mobile user to whom the communications information is directed, to provide a roaming and handoff function between cells.
A personal communications network (PCN) is a mobile wireless telephone service for local use in environments in which the use of digital cellular communication is impracticable. Such environments include areas in which buildings or other structures cause undesirable signal transmission characteristics, or areas of high density telephony use. For example, a personal communications network may be configured as a private PCN (or radio PBX), to serve mobile users within an office building or plant, as a public PCN, for the high density telephony use areas, such as downtown areas, malls, and airports, or as a residential PCN where homes and condominiums are served by a local radio loop to outside base stations.
Numerous techniques have heretofore been proposed in the U.S. and Europe for the service of personal communications networks. These approaches typically involve a network of small cells which are served by a low-power radio interface. However, such systems generally require a radio interface different from that used in the digital cellular network. For example, personal communications systems are proposed that employ radio interfaces using Code Division Multiple Access (CDMA), while other systems (CT-2 and DECT) have adopted relatively wide band Time Division Multiple Access (TDMA) with Time Division Duplex (TDD) interfaces.
In addition, the allocation of frequency bands different from those committed to digital cellular communications has generally been required in such systems due to the scarcity of spectrum envisaged for PCNs sharing the cellular spectrum.
Thus, the basic disadvantages of the previously proposed PCN systems are that they require the use of different communications units for personal and cellular communications, different system infrastructures, and the allocation of different frequency bands.
Accordingly, from the user's perspective, it would be desirable to adapt PCN systems to cellular to eliminate the need for different communications units in different environments. For instance, cellular-based PCNs could enable the use of cellular portable units in the office, and new personal units could be made cellular-ready by car-based RF power boosters or by adherence to stringent distance limitations relative to the cellular base stations.
The major consideration in the adaptation of PCN to cellular to achieve the above advantages is the ability of the frequency spectrum currently allocated to cellular to support both cellular traffic and the multitude of localized high traffic densities usually associated with PCNs.